A method is widely known in which acrylonitrile is produced by a vapor phase catalytic ammoxidation reaction using propylene, ammonia, and molecular oxygen (oxygen-containing gas) as a starting material in a fluidized bed reactor. In particular, a composite oxide catalyst containing molybdenum and bismuth is useful in the ammoxidation reaction and thus industrially widely used.
Hitherto, a large number of researches have been made on the composite oxide catalyst containing molybdenum and bismuth and various catalysts have been proposed.
For example, a catalyst containing molybdenum and bismuth is disclosed in Patent Document 1. In addition, a catalyst containing molybdenum, bismuth, and iron is disclosed in Patent Document 2. Moreover, a catalyst further containing other components in addition to molybdenum and bismuth is disclosed in Patent Documents 3 to 6.
In addition, a method for producing a composite oxide catalyst containing molybdenum and bismuth is disclosed in Patent Documents 7 to 9.
However, the ammoxidation reaction is typically carried out at a high temperature of 400 to 500° C. For that reason, the molybdenum component or the like in the catalyst is easily volatilized and thus the catalyst performance tends to decrease time dependently.
Therefore, as a countermeasure, a method is disclosed in, for example, Patent Document 10 in which molybdenum oxide is supported on an inert support and this is reacted by mixing with a catalyst. In addition, a method is disclosed in Patent Document 11 in which a reactivating agent containing molybdenum, phosphorus, chromium, bismuth, and the like is added to the catalyst. Moreover, a method using a molybdenum-enriched catalyst is disclosed in Patent Documents 12 to 15. Furthermore, a method is disclosed in Patent Documents 16 to 18 in which the reaction is performed while adding a molybdenum-containing compound which is not supported on a support.